Magnetic resonance imaging studies of spontaneous capillary water imbibition in aerated gypsum

International audienceIn this paper we investigate both capillary water imbibition and the sorptivity of aerated gypsum plaster, and how these sorption characteristics are related to the pore structure of the material. These characteristics are examined by monitoring mass change using the conventional gravimetric method and by obtaining water content profiles using nondestructive magnetic resonance imaging (MRI) techniques during capillary imbibition of water. Here, three different gypsum samples are investigated: one non-aerated reference gypsum sample and two aerated gypsum samples produced with different volumetric air fractions. The capillary water absorption into the reference sample follows t 1/2 kinetics (Fickian diffusion), where t is the time of ingress. However, in the aerated gypsum samples there are deviations from t 1/2 kinetics. The MRI results show unambiguously that two wetting fronts advance through the aerated structure ; an observation that cannot be made from the gravimetric data alone. The water content profiles of the aerated gypsum samples are therefore analysed by treating them as the sum of two separate absorption processes using Sharp Front (SF) analysis. The capillary water absorption properties of this material are well described as a parallel combination of fast absorption into fine matrix pores and slow absorption into a modified structure of matrix pores inter-connected to air voids introduced into the slurry by aeration. PACS 47.56.+r. flows through porous media PACS 47.55.nb. capillary and thermocapillary flow

Thermoluminescence du quartz naturel et artificiel pur ou dopé avec des ions Fe++ et Fe+++. Application à la datation des poteries

The thermoluminescence observed on samples of pottery and leading to their archeological dating is a result of the presence of quartz particles originally enclosed in the clay. We offer a study of the thermoluminescence of samples of synthetic mono-crystalline quartz doped in with impurities and apply the results to a new dating technique, the “DATE” method, based upon difference in time attenuation of the emissions.La thermoluminescence constatée sur les échantillons de poteries et conduisant à la datation archéologique de celles-ci, est due aux inclusions de quartz initialement contenues dans l’argile. Nous présentons une étude de la thermoluminescence d’échantillons de quartz monocristallin synthétique dans lesquels des impuretés ont été volontairement ajoutées et appliquons les résultats â une nouvelle technique de datation, la méthode DATE (différence d'atténuation temporelle des émissions).La termoluminiscencia constatada en muestras de cerámica permite una datación arqueológica; es debida a las inclusiones de cuarzo inicialmente contenidas en la arcilla. Se presenta un estudio de la termoluminiscencia de muestras de cuarzo monocristalino sintético en las cuales han sido colocadas voluntariamente impurezas; se han aplicado los resultados de una nueva técnica de fechado, el método DATE (Diferencia de atenuación temporal de emisiones).Roman A., Decamps E. A. Thermoluminescence du quartz naturel et artificiel pur ou dopé avec des ions Fe++ et Fe+++. Application à la datation des poteries. In: Bulletin de l'Institut Français d’Études Andines, tome 7, N°3-4, 1978. pp. 153-164

Datation par thermoluminescence

Since 1953, a number of scientists have been concerned with the use of thermoluminescence for the dating of burned or fired minerals. After recalling some of the physical principles of thermoluminescence, this paper describes that dating process with emphasis upon the working of the thermoluminescent phenomenon in a piece of earthenware. The dose of irradiation received by the material being in direct ratio to the time elapsed since the "archeological zero", it is possible to determine the "archeological dose" and, after calculating the annual dose of irradiation, infer from it the age of the sample. Practically, however, carrying out such a set of measurements is arduous matter. In a forthcoming paper, E. A. Decamps and A. Roman will present some results about the thermoluminescence of samples of pure or doped natural quartz and the perfecting of a new dating process.Depuis 1953, de nombreux chercheurs se sont intéressés à la datation par thermoluminescence de minéraux anciennement brûlés ou cuits. Dans ce travail, après avoir rappelé quelques principes physiques de la thermoluminescence, on présente cette méthode de datation en mettant l'accent sur le mécanisme thermoluminescent dans une poterie. Ainsi la dose d’irradiation reçue par le matériau étant proportionnelle au temps écoulé depuis le "zéro archéologique", il est possible de déterminer "la dose archéologique" et d'en déduire l'âge de l’échantillon après avoir calculé la dose d’irradiation annuelle. La réalisation pratique d’un tel ensemble de mesure est cependant très ardue. Dans un prochain article, E. A. Decamps et A. Roman montreront des résultats relatifs à la thermoluminescence d’échantillons de quartz naturels, purs et dopés et la mise au point d’une nouvelle méthode de datation.Desde 1953, muchos investigadores se han interesado en la datación por termoluminiscencia de minerales antiguamente quemados o cocidos. Dentro de este trabajo, luego de haber recordado algunos principios físicos de la termoluminiscencia, se presenta este método de datación poniendo mayor atención en el mecanismo termoluminiscente en una vasija de metal o de barro. Siendo proporcional la dosis de irradiación recibida al tiempo transcurrido desde el "cero arqueológico", es posible determinar "la dosis arqueológica", y deducir la edad de la muestra luego de haber calculado la dosis de irradiación anual. La realización práctica de un trabajo de tal dimensión es sin embargo muy ardua. En un próximo artículo, E. A. Decamps y A. Roman presentarán los resultados relativos a la termoluminiscencia de muestras de cuarzo naturales, puras y dopadas y la elaboración de un nuevo método de datación.Abba F., Decamps E. A., Brun Patrice, Bombre F. Datation par thermoluminescence. In: Bulletin de l'Institut Français d’Études Andines, tome 5, N°3-4, 1976. pp. 91-104

He and Cr effects on radiation damage formation in ion-irradiated pure iron and Fe-5.40 wt.% Cr: A transmission electron microscopy study

The first walls of future fusion reactors will be exposed to 14 MeV neutron irradiation. In order to gain insight into their radiation resistance, model materials (a high purity iron and a Fe-5.40 wt.% Cr alloy) have been ion-irradiated in the JANNuS facility to high doses with and without helium. The materials were self-ion-irradiated at 500 degrees C up to similar to 100 displacements per atom (dpa) with gas implantation rates equal to 0, 2.5 and 25 appm He dpa(-1). He and Cr effects on the radiation damage formation have been studied at the microscopic scale by transmission electron microscopy. In pure Fe, a coarse dislocation network was observed after irradiation, irrespective of helium implantation rate. Concerning the V-containing features (nanobubbles or cavities), few large cavities were observed in pure iron irradiated without helium. The main effect of helium implantation was to increase their density and diminish their size. The main effect of chromium was to reduce the swelling for all the He implantation rates. Furthermore, in both materials, the cavity formation was mainly heterogeneous. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved

Single- and dual-beam in situ irradiations of high-purity iron in a transmission electron microscope: Effects of heavy ion irradiation and helium injection

In order to study the effects of 14 MeV neutron irradiation on materials used in the first walls of future fusion reactors, high-purity iron was ion-irradiated with and without helium in the JANNuS facility. Thin foils of high-purity iron were dual-beam irradiated in situ in a transmission electron microscope using 1 MeV Fe+ and 15 keV He+ ions. Several important results regarding dislocation loops and helium bubbles were obtained. For example, it was demonstrated that dislocation loops with a0 〈0 1 0〉 type Burgers vectors are glissile and can move and eliminate at the surface of the thin foil at 500 °C. A comparison of irradiations with and without helium showed that helium atoms reduce the mobility of dislocation loops in pure iron irradiated at 500 °C. Also, we demonstrated that the heterogeneous formation of bubbles inside dislocation loops found previously is also present for helium implantation rates of ∼80 atomic parts per million (appm) He/displacements per atom (dpa)

Synthèse de molécules d’intérêt biologique. Contribution à la synthèse des bastadines

Synthesis of molecules of biological interest. Contribution to the synthesis of bastadins. The metabolites are a biochemical area whose interest is in constant progression. Indeed, these molecules are biologically active and are used in therapeutic treatments. This work focuses on the solid phase synthesis of macromolecules from metabolites synthesized by an enzyme. The development of Erwinia herbicola cultures has achieved the synthesis of metabolites: L-dopa and dopamine. From a medical point of view, these molecules have a particular interest since they act as neurotransmitters in human nerve cells. Through a chemical reaction scheme from dopamine, we are interested in solid phase synthesis of a macromolecule like bastadin (bis-diarylethers). This molecule of natural origin is produced by marine sponge, and has anti-angiogenic and antimicrobial properties. A complete scheme of chemical synthesis of bastadines was developed by Couladouros et al. (2005) in homogeneous phase, but it requires a lot of steps with an overall yield of synthesis extremely low (less than 1%). This work aims to develop and implement a part of original scheme for the synthesis of this molecule in heterogeneous phase from dopamine. Indeed the fragment left of the bastadine can be achieved via a coupling reaction in basic medium between dopamine modified on solid support and a diaryliodonium salt

SPIDER ion source and extraction power supplies- An update of the design of the bias circuits after four years of operation

SPIDER, the ion source prototype for ITER neutral beam injectors, has been in operation since 2018. The experiment includes a system of Ion Source and Extraction Power Supplies (ISEPS), whose design dates back to 2011. Since then the experience gained has led to substantial changes, the most dramatic modification being the complete replacement of the radiofrequency power supply, described elsewhere. This contribution details operating experience and calculations that have led to defining new requirements for a specific subset of power supplies, the bias power supplies.The bias power supplies perform the function of filtering out electrons extracted together with the negative ions and in the original 2011 ISEPS design are single quadrant resonant converters. For the two bias power supplies, the picture resulting from the review described in the paper is a substantial redesign, with the ability to operate in four quadrants and a twofold increase of the rated output voltage the most significant new specifications

Towards large scale aligned carbon nanotube composites: an industrial safe-by-design and sustainable approach

International audienceWe present the main results demonstrating the feasibility of high surface (> A4 format size) semi-industrial fabrication of composites embedding VACNT in organic matrices. The process of growing VACNT exhibits several advantages regarding safety issues: integrating de facto a safe collecting procedure on the substrate, avoiding additional preparation steps and simplifying handling and protection by impregnation into a matrix. The following steps of the overall process: VACNT carpet functionalization, alignment control and impregnation, can be processed on-line in a closed and safe continuous process and lead to dramatically reduced direct nanotube exposure for workers and users. This project opens the route to a continuous, roll-to-roll, safer, cost-effective and green industrial process to manufacture composites with controlled and aligned greener "black" carbon nanotubes